M.K. Purkait

ADSORPTION CHARACTERISTICS OF BRILLIANT GREEN DYE ON KAOLIN

Experimental investigations were carried out to adsorb toxic brilliant green dye from aqueous medium using kaolin as an adsorbent. Characterization of kaolin is done by measuring: (i) particle size distribution using particle size analyzer, (ii) BET surface area using BET surface analyzer, and (iii) structural analysis using X-ray diffractometer. The effects of initial dye concentration, contact time, kaolin dose, stirring speed, pH and temperature were studied for the adsorption of brilliant green in batch mode. Adsorption experiments indicate that the extent of adsorption is strongly dependent on pH of solution. Free energy of adsorption (DeltaG0), enthalpy (DeltaH0) and entropy (DeltaS0) changes are calculated to know the nature of adsorption. The calculated values of DeltaG0 at 299K and 323K indicate that the adsorption process is spontaneous. The estimated values of DeltaH0 and DeltaS0 both show the negative sign, which indicate that the adsorption process is exothermic and the dye molecules are organized on the kaolin surface in less randomly fashion than in solution. The adsorption kinetic has been described by first-order, pseudo-second-order and intra-particle-diffusion models. It was observed that the rate of dye adsorption follows pseudo-second-order model for the dye concentration range studied in the present case. Standard adsorption isotherms were used to fit the experimental equilibrium data. It was found that the adsorption of brilliant green on kaolin follows the Langmuir adsorption isotherm.

Nanofiltration of textile plant effluent for color removal and reduction in COD

Abstract A membrane based separation process (nanofiltration, NF) is used to treat the effluent from a textile plant. The dye mixture contains reactive black dye (Cibacron Black B) and reactive red dye (Cibacron Red RB). An organic membrane with molecular weight cut-off of 400 is used for the experiments. The experiments are conducted in an unstirred batch and a rectangular cross flow cell. Separations with retentions up to 94 and 92% of the two dyes are achieved respectively in the cross flow cell where steady state is attained quickly. It is important to note that NF techniques achieve a sharp reduction in chemical oxygen demand (COD), (up to 94% in cross flow cell), as the dyes are removed from the permeate. A parametric study of the separation process is undertaken to characterize the effects of the operating variables, e.g., trans-membrane pressure, dye concentration in the feed and cross flow velocity in case of cross flow NF.

Treatment of fluoride containing drinking water by electrocoagulation using monopolar and bipolar electrode connections.

Electrocoagulation was investigated for the effective removal of fluoride from drinking water. Different initial concentrations (2-10 mg L(-1)) of fluoride were considered for the experiment. Two different electrode connections (monopolar and bipolar) were examined for choosing the better alternative in order to intensify the performance of the process. It was observed that the removal of fluoride was better for bipolar connection than for monopolar connection. The final recommendable limit of fluoride (1 mg L(-1)) was obtained in 30 min at 625 Am(-2) using bipolar connection. The corrosion of electrodes as well as the sludge formed during the process was estimated for the bipolar connection. Thickness of film generated on the electrode surfaces in bipolar connection was also estimated at different current densities as well as for different initial fluoride concentrations. By-products obtained from the electrocoagulation bath were analyzed using SEM, EDAX, FTIR and XRD and explained. Comparative cost estimation for both electrode connections was adopted and presented as well. Total operating costs for monopolar and bipolar connections were 0.38 and 0.62 US

Removal of Fe(II) from tap water by electrocoagulation technique.

m(-3), respectively, for the initial fluoride concentration of 10 mg L(-1). These findings might be useful in order to treat the fluoride contaminated water for drinking.

Novel strategy for synthesis of magnetic dummy molecularly imprinted nanoparticles based on functionalized silica as an efficient sorbent for the determination of acrylamide in potato chips: Optimization by experimental design methodology

Electrocoagulation (EC) is a promising electrochemical technique for water treatment. In this work electrocoagulation (with aluminum as electrodes) was studied for iron Fe(II) removal from aqueous medium. Different concentration of Fe(II) solution in tap water was considered for the experiment. During EC process, various amorphous aluminum hydroxides complexes with high sorption capacity were formed. The removal of Fe(II) was consisted of two principal steps; (a) oxidation of Fe(II) to Fe(III) and (b) subsequent removal of Fe(III) by the freshly formed aluminum hydroxides complexes by adsorption/surface complexation followed by precipitation. Experiments were carried out with different current densities ranging from 0.01 to 0.04 A/m2. It was observed that the removal of Fe(II) increases with current densities. Inter electrode distance was varied from 0.005 to 0.02 m and was found that least inter electrode distance is suitable in order to achieve higher Fe(II) removal. Other parameters such as conductivity, pH and salt concentration were kept constant as per tap water quality. Satisfactory iron removal of around 99.2% was obtained at the end of 35 min of operation from the initial concentration of 25 mg/L Fe(II). Iron concentration in the solution was determined using Atomic absorption spectrophotometer. By products obtained from the electrocoagulation bath were analyzed by SEM image and corresponding elemental analysis (EDAX). Cost estimation for the electrocoagulation was adopted and explained well. Up to 15 mg/L of initial Fe(II) concentration, the optimum total cost was 6.05 US

Application of central composite design for simultaneous removal of methylene blue and Pb2+ ions by walnut wood activated carbon

/m3. The EC process for removing Fe(II) from tap water is expected to be adaptable for household use.

Simultaneous ultrasound-assisted removal of sunset yellow and erythrosine by ZnS:Ni nanoparticles loaded on activated carbon: Optimization by central composite design

This study discusses a novel and simple method for the preparation of magnetic dummy molecularly imprinted nanoparticles (MDMINPs). Firstly, Fe3O4 magnetic nanoparticles (MNPs) were synthesized as a magnetic component. Subsequently, MDMINPs were constructed via the sol-gel strategy using APTMS as the functional monomer. Urethane was considered as dummy template to avoid residual template and TEOS as the cross linker. The prepared MDMINPs were used for the pre-concentration of acrylamide from potato chips. Quantification was carried out by high performance liquid chromatography with UV detection (HPLC-UV). The impact of influential variables such as pH, amount of sorbent, sonication time and eluent volume were well investigated and optimized using a central composite design. The particles had excellent magnetic property and high selectivity to the targeted molecule. In optimized conditions, the recovery ranged from 94.0% to 98.0% with the detection limit of 0.35µgkg(-1).

Kinetic and Equilibrium Studies on the Adsorption of Crystal Violet Dye using Kaolin as an Adsorbent

Activated carbon was prepared from walnut wood which was locally available, non-toxic, abundant and cheap. This new adsorbent was characterized using BET, FTIR and SEM. Point of zero charge (pHpzc) and oxygen containing functional groups were also determined. The prepared adsorbent was applied for simultaneous removal of Pb(2+) ions and methylene blue (MB) dye from aqueous solution. The prominent effect and interaction of variables such as amount of adsorbent, contact time, concentration of MB and Pb(2+) ions were optimized by central composite design. The equilibrium data obtained at optimum condition were fitted to conventional isotherm models and found that Langmuir model was the best fitted isotherm. Kinetic data were fitted using various models. It was revealed that the adsorption rate follows pseudo-second order kinetic model and intraparticle diffusion model.

Cadmium telluride nanoparticles loaded on activated carbon as adsorbent for removal of sunset yellow.

The present study focused on the simultaneous ultrasound-assisted removal of sunset yellow and erythrosine dyes from aqueous solutions using ZnS:Ni nanoparticles loaded on activated carbon (ZnS:Ni-NP-AC) as an adsorbent. ZnS:Ni nanoparticles were synthesized and characterized using different techniques such as FESEM, XRD and TEM. The effects of various parameters such as sonication time, pH, initial dye concentrations and adsorbent dose on the percentage of dye removal were investigated. Parameters were optimized by central composite design (CCD) combined with response surface methodology (RSM) and desirability function (DF). A good agreement between experimental and predicted values was observed. The ultrasound-assisted adsorbent (0.04 g) was capable of high percentage removal (98.7% and 99.6%) of sunset yellow and erythrosine in short time (3.8 min).

Simultaneous removal of methylene blue and Pb2+ ions using ruthenium nanoparticle-loaded activated carbon: response surface methodology

Abstract Experimental investigations are carried out to adsorb toxic crystal violet dye from aqueous medium using kaolin as an adsorbent. Characterization of kaolin is done by measuring i. particle size distribution using particle size analyzer, ii. BET surface area using BET surface analyzer, iii. structural analysis using X ray diffractometer, and iv. microscopic analysis using scanning electron microscope. The effects of initial dye concentration, contact time, kaolin dose, stirring speed, pH, and temperature are studied for the adsorption of crystal violet in batch mode. Adsorption experiments indicate that the extent of adsorption is strongly dependent on the pH of the solution. Free energy of adsorption (ΔG o ), enthalpy (ΔH o ), and entropy (ΔS o ) changes are calculated to know the nature of adsorption. The calculated values of ΔG o are −4.11 and −4.48 kJ/mol at 295 K and 323 K, respectively, for 20 mg/L of dye concentration, which indicates that the adsorption process is spontaneous. The estimated values of ΔH o and ΔS o show the negative and positive sign, respectively, which indicate that the adsorption process is exothermic and the dye molecules are organized on the kaolin surface in more random fashion than in solution. The adsorption kinetic has been described by pseudo first order, pseudo second order and intra‐particle diffusion models. It is observed that the rate of dye adsorption follows pseudo second order model for the dye concentration range studied in the present case. Standard adsorption isotherms are used to fit the experimental equilibrium data. It is found that the adsorption of crystal violet on kaolin follows the Langmuir adsorption isotherm.